This invention relates to a process for the preparation of carbon black products. The process involves reacting a diazonium salt with a carbon black to yield a carbon black product having an organic group attached to the carbon black. The invention also relates to new carbon black products and their uses.
Much effort has been expended over the last several decades to modify the surface chemistry of carbon black. While it is possible to deposit physically adsorbed material onto the surface of carbon black, permanently changing the surface chemistry of carbon black is substantially more difficult.
Some processes for chemically changing the surface of carbon black are known and used commercially. For example, it is well known that a carbon black surface can be oxidized with a variety of treating agents. Surface oxidation is used to make some commercial products. Sulfonation using sulfuric acid or chlorosulfuric acid and halogenation of a carbon black surface are also known. Some known methods for grafting polymers to the carbon black surface are reviewed by Tsubakowa in Polym. Sci., Vol. 17, pp 417-470, 1992. See also U.S. Pat. No. 4,014,844 which grafts polymers onto carbon black by contacting the carbon black with the polymer and heating.
U.S. Pat. No. 3,479,300 describes carbon catalyst compositions and a process for their production. The catalyst compositions are prepared by treating carbon particles with an alkali or alkaline earth metal and subsequently treating the resulting carbon/metal composition with a solvating ether. The carbon portions of the catalytic compositions can be reacted with various reagents, including organic compounds, to produce carbon compositions.
U.S. Pat. No. 3,043,708 describes modified carbon blacks having hydrocarbon groups chemically attached to the surface of the carbon black. The modified carbon blacks are prepared by reacting carbon black with an alkylating agent in the presence of a Friedel-Crafts type reaction catalyst. The hydrocarbon groups which reportedly can attach to the surface of the carbon black include aliphatic and aromatic groups. A modified carbon black containing aryl groups attached to the surface of a carbon black is reported as being preparable by reacting a halogenated carbon black with an aromatic hydrocarbon in the presence of a Friedel-Crafts type catalyst. U.S. Pat. No. 3,025,259 describes rubber compositions containing the modified carbon blacks of U.S. Pat. No. 3,043,708.
U.S. Pat. No. 3,335,020 describes modified carbon blacks where the carbon black is treated with benzene which is then polymerized on the carbon black. To prepare these modified carbon blacks, benzene and carbon black are mixed with a Lewis Acid catalyst under anhydrous conditions for about ten minutes. The benzene on the carbon black is then polymerized to parapolyphenyl by means of a combination co-catalyst-oxidizing agent and is reportedly thereby bonded to the carbon black.
U.S. Pat. Nos. 2,502,254 and 2,514,236 describe the manufacture of pigments containing carbon black. U.S. Pat. No. 2,502,254 reports that highly dispersed pigments suitable for mass pigmentation of viscose can be obtained by generating an azo pigment in the presence of carbon black.
The pigment is produced by coupling a diazotized amine and another usual intermediate for a yellow, orange, or red pigment in the presence of carbon black in one or the other of the aqueous solutions of which the mixing brings about the coupling. U.S. Pat. No. 2,514,236 reports that this process can also prepare a chocolate brown pigment by coupling one molecular proportion of a tetrazotized benzidine with two molecular proportions of an arylmethyl pyrazolone in the presence of carbon black.
PCT patent application No. WO 92/13983 describes a process for modifying the surfaces of carbon-containing materials by electrochemical reduction of diazonium salts. The process is reportedly applicable, in particular, to carbon plates and carbon fibers for composite materials. Carbon-containing materials modified by the process are also described. Electrochemical reduction of diazonium salts containing funcitonalized aryl radicals to covalently modify carbon surfaces is also described in Delmar et al., J. Am. Chem. Soc. 1992, 114, 5883-5884.
According to WO 92/13983, the process for modifying the surface of a carbon-containing material consists of grafting an aromatic group to the surface of this material by electrochemical reduction of a diazonium salt including this aromatic group. The carbon-containing material is placed in contact with a diazonium salt solution in an aprotic solvent and is negatively charged with respect to an anode which is also in contact with the diazonium salt solution. Use of a protic solvent is reported to prevent the electrochemical process from producing the intended product as a result of reducing the diazonium triple bond to yield a hydrazine.
Despite the technology discussed above, there remains a need to modify the surface chemistry of carbon black and impart desired properties to the carbon black.
Accordingly, the present invention relates to processes for preparing a carbon black product having an organic group attached to the carbon black. One process comprises the step of reacting at least one diazonium salt with a carbon black in the absence of an externally applied electric current sufficient to reduce the diazonium salt. Another process comprises the step of reacting at least one diazonium salt with a carbon black in a protic reaction medium.
Other embodiments of the invention relate to novel carbon black products, which may be prepared according to a process of the invention. The carbon black products may be used in the same applications as conventional carbon blacks. Such uses include, but are not limited to, plastic compositions, aqueous inks, aqueous coatings, rubber compositions, paper compositions, and textile compositions.
The description which follows sets out additional features and advantages of the invention. These functions will be apparent from that description or may be learned by practice of the invention as described. The objectives and other advantages will be realized and attained by the processes, products, and compositions particularly pointed out in the description below and the appended claims.
Processes for Preparing a Carbon Black Product
A first embodiment of the invention provides processes for preparing a carbon black product having an organic group attached to the carbon black. One process involves the reaction of at least one diazonium salt with a carbon black in the absence of an externally applied current sufficient to reduce the diazonium salt. That is, the reaction between the diazonium salt and the carbon black proceeds without an external source of electrons sufficient to reduce the diazonium salt. Mixtures of different diazonium salts may be used in the process of the invention. This process can be carried out under a variety of reaction conditions and in any type of reaction medium, including both protic and aprotic solvent systems or slurries.
In another process, at least one diazonium salt reacts with a carbon black in a protic reaction medium. Mixtures of different diazonium salts may be used in this process of the invention. This process can also be carried out under a variety of reaction conditions.
Preferably, in both processes, the diazonium salt is formed in situ. If desired, in either process, the carbon black product can be isolated and dried by means known in the art. Furthermore, the resultant carbon black product can be treated to remove impurities by known techniques. The various preferred embodiments of these processes are discussed below and are shown in the examples.
Any carbon black may be used in the processes of this invention. The resulting carbon black products are useful in applications known for conventional carbon blacks. The properties of the carbon blacks are selected based upon the intended application. More importantly, the processes of this invention can be used to provide carbon black products having advantageous properties not associated with conventional carbon blacks.
The processes of the invention can be carried out under a wide variety of conditions and in general are not limited by any particular condition. The reaction conditions must be such that the particular diazonium salt is sufficiently stable to allow it to react with the carbon black. Thus, the processes can be carried out under reaction conditions where the diazonium salt is short lived. As the examples below illustrate, the reaction between the diazonium salt and the carbon black occurs, for example, over a wide range of pH and temperature. The processes can be carried out at acidic, neutral, and basic pH. Preferably, the pH ranges from about 1 to 9. The reaction temperature may preferably range from 0xc2x0 C. to 100xc2x0 C.
Diazonium salts, as known in the art, may be formed for example by the reaction of primary amines with aqueous solutions of nitrous acid. A general discussion of diazonium salts and methods for their preparation is found in Morrison and Boyd, Organic Chemistry, 5th Ed., pp. 973-983, (Allyn and Bacon, Inc. 1987) and March, Advanced Organic Chemistry: Reactions, Mechanisms, and Structures, 4th Ed., (Wiley, 1992). According to this invention, a diazonium salt is an organic compound having one or more diazonium groups.
In the processes of the invention, the diazonium salt may be prepared prior to reaction with the carbon black or, more preferably, generated in situ using techniques known in the art. In situ generation also allows the use of unstable diazonium salts such as alkyl diazonium salts and avoids unnecessary handling or manipulation of the diazonium salt. In particularly preferred processes of this invention, both the nitrous acid and the diazonium salt are generated in situ. Each of these variations is shown in the examples below.
A diazonium salt, as is known in the art, may be generated by reacting a primary amine, a nitrite and an acid. The nitrite may be any metal nitrite, preferably lithium nitrite, sodium nitrite, potassium nitrite, or zinc nitrite, or any organic nitrite such as for example isoamylnitrite or ethylnitrite. The acid may be any acid, inorganic or organic, which is effective in the generation of the diazonium salt. Preferred acids include nitric acid, HNO3, hydrochloric acid, HCl, and sulfuric acid, H2SO4.
The diazonium salt may also be generated by reacting the primary amine with an aqueous solution of nitrogen dioxide. The aqueous solution of nitrogen dioxide, NO2/H2O, provides the nitrous acid needed to generate the diazonium salt.
Generating the diazonium salt in the presence of excess HCl may be less preferred than other alternatives because HCl is corrosive to stainless steel. Generation of the diazonium salt with NO2/H2O has the additional advantage of being less corrosive to stainless steel or other metals commonly used for reaction vessels. Generation using H2SO4/NaNO2 or HNO3/NaNO2 are also relatively non-corrosive.
In general, generating a diazonium salt from a primary amine, a nitrite, and an acid requires two equivalents of acid based on the amount of amine used. In an in situ process, the diazonium salt can be generated using one equivalent of the acid. When the primary amine contains a strong acid group, adding a separate acid may not be necessary in the processes of the invention. The acid group or groups of the primary amine can supply one or both of the needed equivalents of acid. When the primary amine contains a strong acid group, preferably either no additional acid or up to one equivalent of additional acid is added to a process of the invention to generate the diazonium salt in situ. A slight excess of additional acid may be used. One example of such a primary amine is para-aminobenzenesulfonic acid (sulfanilic acid). Others are shown in the examples below.
In general, diazonium salts are thermally unstable. They are typically prepared in solution at low temperatures, such as 0-5xc2x0 C., and used without isolation of the salt. Heating solutions of some diazonium salts may liberate nitrogen and form either the corresponding alcohols in acidic media or the organic free radicals in basic media.
However, to accomplish the process of the invention, the diazonium salt need only be sufficiently stable to allow reaction with the carbon black. Thus, the processes of the present invention can be carried out with some diazonium salts otherwise considered to be unstable and subject to decomposition. Some decomposition processes may compete with the reaction between the carbon black and the diazonium salt and may reduce the total number of organic groups attached to the carbon black. Further, the reaction may be carried out at elevated temperatures where many diazonium salts may be susceptible to decomposition. Elevated temperatures may also advantageously increase the solubility of the diazonium salt in the reaction medium and improve its handling during the process. However, elevated temperatures may result in some loss of the diazonium salt due to other decomposition processes.
The processes of the invention can be accomplished by adding the reagents to form the diazonium salt in situ, to a suspension of carbon black in the reaction medium, for example, water. Thus, a carbon black suspension to be used may already contain one or more reagents to generate the diazonium salt and the process of the invention accomplished by adding the remaining reagents. Some permutations of such processes are shown in the examples below.
Reactions to form a diazonium salt are compatible with a large variety of functional groups commonly found on organic compounds. Thus, only the availability of a diazonium salt for reaction with a carbon black limits the processes of the invention.
The processes of this invention can be carried out in any reaction medium which allows the reaction between the diazonium salt and the carbon black to proceed. Preferably, the reaction medium is a solvent-based system. The solvent may be a protic solvent, an aprotic solvent, or a mixture of solvents. Protic solvents are solvents, like water or methanol, containing a hydrogen attached to an oxygen or nitrogen and thus are sufficiently acidic to form hydrogen bonds. Aprotic solvents are solvents which do not contain an acidic hydrogen as defined above. Aprotic solvents include, for example, solvents such as hexanes, tetrahydrofuran (THF), acetonitrile, and benzonitrile. For a discussion of protic and aprotic solvents see Morrison and Boyd, Organic Chemistry, 5th Ed., pp. 228-231, (Allyn and Bacon, Inc. 1987).
The processes of this invention are preferably carried out in a protic reaction medium, that is, in a protic solvent alone or a mixture of solvents which contains at least one protic solvent. Preferred protic media include, but are not limited to water, aqueous media containing water and other solvents, alcohols, and any media containing an alcohol, or mixtures of such media.
According to the processes of the invention, the reaction between a diazonium salt and a carbon black can take place with any type of carbon black, for example, in fluffy or pelleted form. In one embodiment designed to reduce production costs, the reaction occurs during a process for forming carbon black pellets. For example, a carbon black product of the invention can be prepared in a dry drum by spraying a solution or slurry of a diazonium salt onto a carbon black. Alternatively, the carbon black product can be prepared by pelletizing a carbon black in the presence of a solvent system, such as water, containing the diazonium salt or the reagents to generate the diazonium salt in situ. Aqueous solvent systems are preferred. Accordingly, another embodiment of the invention provides a process for forming a pelletized carbon black comprising the steps of: introducing a carbon black and an aqueous slurry or solution of a diazonium salt into a pelletizer, reacting the diazonium salt with the carbon black to attach an organic group to the carbon black, and pelletizing the resulting carbon black having an attached organic group. The pelletized carbon black product may then be dried using conventional techniques.
In general, the processes of the invention produce inorganic by-products, such as salts. In some end uses, such as those discussed below, these by-products may be undesirable. Several possible ways to produce a carbon black product according to a process of the invention without unwanted inorganic by-products or salts are as follows:
First, the diazonium salt can be purified before use by removing the unwanted inorganic by-product using means known in the art. Second, the diazonium salt can be generated with the use of an organic nitrite as the diazotization agent yielding the corresponding alcohol rather than an inorganic salt. Third, when the diazonium salt is generated from an amine having an acid group and aqueous NO2, no inorganic salts are formed. Other ways may be known to those of skill in the art.
In addition to the inorganic by-products, a process of the invention may also produce organic by-products. They can be removed, for example, by extraction with organic solvents. Other ways may be known to those of skill in the art.
Carbon Black Products
The reaction between a diazonium salt and a carbon black according to a process of this invention forms a carbon black product having an organic group attached to the carbon black. The diazonium salt may contain the organic group to be attached to the carbon black. Thus, the present invention relates to carbon black products having an organic group attached to the carbon black, particularly those prepared by a process of this invention. It may be possible to produce the carbon black products of this invention by other means known to those skilled in the art.
The organic group may be an aliphatic group, a cyclic organic group, or an organic compound having an aliphatic portion and a cyclic portion. As discussed above, the diazonium salt employed in the processes of the invention can be derived from a primary amine having one of these groups and being capable of forming, even transiently, a diazonium salt. The organic group may be substituted or unsubstituted, branched or unbranched. Aliphatic groups include, for example, groups derived from alkanes, alkenes, alcohols, ethers, aldehydes, ketones, carboxylic acids, and carbohydrates. Cyclic organic groups include, but are not limited to, alicyclic hydrocarbon groups (for example, cycloalkyls, cycloalkenyls), heterocyclic hydrocarbon groups (for example, pyrrolidinyl, pyrrolinyl, piperidinyl, morpholinyl, and the like), aryl groups (for example, phenyl, naphthyl, anthracenyl, and the like), and heteroaryl groups (imidazolyl, pyrazolyl, pyridinyl, thienyl, thiazolyl, furyl, indolyl, and the like). As the steric hinderance of a substituted organic group increases, the number of organic groups attached to the carbon black from the reaction between the diazonium salt and the carbon black may be diminished.
When the organic group is substituted, it may contain any functional group compatible with the formation of a diazonium salt. Preferred functional groups include, but are not limited to, R, OR, COR, COOR, OCOR, carboxylate salts such as COOLi, COONa, COOK, COOxe2x88x92NR4+, halogen, CN, NR2, SO3H, sulfonate salts such as SO3Li, SO3Na, SO3K, SO3xe2x88x92NR4+, OSO3H, OSO3xe2x88x92salts, NR (COR), CONR2, NO2, PO3H2, phosphonate salts such as PO3HNa and PO3Na2, phosphate salts such as OPO3HNa and OPO3Na2, N=NR, NR3+Xxe2x88x92, PR3+Xxe2x88x92, SkR, SSO3H, SSO3xe2x88x92salts, SO2NRRxe2x80x2, SO2SR, SNRRxe2x80x2, SNQ, SO2NQ, CO2NQ, S-(1,4-piperazinediyl)-SR, 2-(1,3-dithianyl) 2-(1,3-dithiolanyl), SOR, and SO2R. R and Rxe2x80x2, which can be the same or different, are independently hydrogen, branched or unbranched C1-C20 substituted or unsubstituted, saturated or unsaturated hydrocarbon, e.g., alkyl, alkenyl, alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkylaryl, or substituted or unsubstituted arylalkyl. The integer k ranges from 1-8 and preferably from 2-4. The anion Xxe2x88x92is a halide or an anion derived from a mineral or organic acid. Q is (CH2)w, (CH2)xO(CH2)z, (CH2)xNR(CH2)z, or (CH2)xS(CH2)z, where w is an integer from 2 to 6 and x and z are integers from 1 to 6.
The carbon black product can comprise a carbon black and at least one organic group having a) an aromatic group and b) a cationic group, wherein at least one aromatic group of the organic group is attached to the carbon black. The organic group can be, for example Xxe2x88x92R3N+CH2COAr, wherein R is a substituted or unsubstituted C1-C10 alkyl, Ar is phenylene or naphthylene, and Xxe2x88x92is a halide or an anion derived from a mineral or organic acid.
A preferred organic group is an aromatic group of the formula AyArxe2x88x92, which corresponds to a primary amine of the formula AyArNH2. In this formula, the variables have the following meanings: Ar is an aromatic radical such as an aryl or heteroaryl group. Preferably, Ar is selected from the group consisting of phenyl, naphthyl, anthracenyl, phenanthrenyl, biphenyl, pyridinyl, benzothiadiazolyl, and benzothiazolyl; A is a substituent on the aromatic radical independently selected from a preferred functional group described above or A is a linear, branched or cyclic hydrocarbon radical (preferably containing 1 to 20 carbon atoms), unsubstituted or substituted with one or more of those functional groups; and y is an integer from 1 to the total number of xe2x80x94CH radicals in the aromatic radical. For instance, y is an integer from 1 to 5 when Ar is phenyl, 1 to 7 when Ar is naphthyl, 1 to 9 when Ar is anthracenyl, phenanthrenyl, or biphenyl, or 1 to 4 when Ar is pyridinyl.
In the above formula, specific examples of R and Rxe2x80x2 are NH2xe2x80x94C6H4xe2x80x94, CH2CH2xe2x80x94C6H4xe2x80x94NH2, CH2xe2x80x94C6H4xe2x80x94NH2, and C6H5.
Another preferred set of organic groups which may be attached to the carbon black are organic groups substituted with an ionic or an ionizable group as a functional group. An ionizable group is one which is capable of forming an ionic group in the medium of use. The ionic group may be an anionic group or a cationic group and the ionizable group may form an anion or a cation.
Ionizable functional groups forming anions include, for example, acidic groups or salts of acidic groups. The organic groups, therefore, include groups derived from organic acids. Preferably, when it contains an ionizable group forming an anion, such an organic group has a) an aromatic group and b) at least one acidic group having a pKa of less than 11, or at least one salt of an acidic group having a pKa of less than 11, or a mixture of at least one acidic group having a pKa of less than 11 and at least one salt of an acidic group having a pKa of less than 11. The pKa of the acidic group refers to the pKA of the organic group as a whole, not just the acidic substituent. More preferably, the pKa is less than 10 and most preferably less than 9. Preferably, the aromatic group of the organic group is directly attached to the carbon black. The aromatic group may be further substituted or unsubstituted, for example, with alkyl groups. More preferably, the organic group is a phenyl or a naphthyl group and the acidic group is a sulfonic acid group, a sulfinic acid group, a phosphonic acid group, or a carboxylic acid group. Examples of these acidic groups and their salts are discussed above. Most preferably, the organic group is a substituted or unsubstituted sulfophenyl group or a salt thereof; a substituted or unsubstituted (polysulfo)phenyl group or a salt thereof; a substituted or unsubstituted sulfonaphthyl group or a salt thereof; or a substituted or unsubstituted (polysulfo) naphthyl group or a salt thereof. A preferred substituted sulfophenyl group is hydroxysulfophenyl group or a salt thereof.
Specific organic groups having an ionizable functional group forming an anion (and their corresponding primary amines for use in a process according to the invention) are p-sulfophenyl (p-sulfanilic acid), 4-hydroxy-3-sulfophenyl (2-hydroxy-5-amino-benzenesulfonic acid), and 2-sulfoethyl (2-aminoethanesulfonic acid). Other organic groups having ionizable functional groups forming anions are shown in the examples below.
Amines represent examples of ionizable functional groups that form cationic groups. For example, amines may be protonated to form ammonium groups in acidic media. Preferably, an organic group having an amine substituent has a pKb of less than 5. Quaternary ammonium groups (xe2x80x94NR3+) and quaternary phosphonium groups (xe2x80x94PR3+) also represent examples of cationic groups. Preferably, the organic group contains an aromatic group such as a phenyl or a naphthyl group and a quaternary ammonium or a quaternary phosphonium group. The aromatic group is preferably directly attached to the carbon black. Quaternized cyclic amines, and even quaternized aromatic amines, can also be used as the organic group. Thus, N-substituted pyridinium compounds, such as N-methyl-pyridyl, can be used in this regard. Examples of organic groups include, but are not limited to, (C5H4N)C2H5+, C6H4(NC5H5)+, C6H4COCH2N(CH3)3+, C6H4COCH2(NC5H5)+, (C5H4N)CH3+, and C6H4CH2N(CH3)3+.
An advantage of the carbon black products having an attached organic group substituted with an ionic or an ionizable group is that the carbon black product may have increased water dispersibility relative to the corresponding untreated carbon black. As shown in the Examples, water dispersibility of a carbon black product increases with the number of organic groups attached to the carbon black having an ionizable group or the number of ionizable groups attached to a given organic group. Thus, increasing the number of ionizable groups associated with the carbon black product should increase its water dispersibility and permits control of the water dispersibility to a desired level. It can be noted that the water dispersibility of a carbon black product containing an amine as the organic group attached to the carbon black may be increased by acidifying the aqueous medium.
Because the water dispersibility of the carbon black products depends to some extent on charge stabilization, it is preferable that the ionic strength of the aqueous medium be less than 0.1 molar. More preferably, the ionic strength is less than 0.01 molar.
When such a water dispersible carbon black product is prepared by a process of the invention, it is preferred that the ionic or ionizable groups be ionized in the reaction medium. The resulting product solution or slurry may be used as is or diluted prior to use. Alternatively, the carbon black product may be dried by techniques used for conventional carbon blacks. These techniques include, but are not limited to, drying in ovens and rotary kilns. Overdrying, however, may cause a loss in the degree of water dispersibility.
In addition to their water dispersibility, carbon black products having an organic group substituted with an ionic or an ionizable group may also be dispersible in polar organic solvents such as dimethylsulfoxide (DMSO), and formamide. In alcohols such as methanol or ethanol, use of complexing agents such as crown ethers increases the dispersibility of carbon black products having an organic group containing a metal salt of an acidic group.
Aromatic sulfides encompass another group of preferred organic groups. Carbon black products having aromatic sulfide groups are particularly useful in rubber compositions. These aromatic sulfides can be represented by the formulas Ar(CH2)qSk(CH2)rArxe2x80x2 or Axe2x80x94(CH2)qSK(CH2)rArxe2x80x3 wherein Ar and Arxe2x80x2 are independently substituted or unsubstituted arylene or heteroarylene groups, Arxe2x80x3 is an aryl or heteroaryl group, k is 1 to 8 and q and r are 0-4. Substituted aryl groups would include substituted alkylaryl groups. Preferred arylene groups include phenylene groups, particularly p-phenylene groups, or benzothiazolylene groups. Preferred aryl groups include phenyl, naphthyl and benzothiazolyl. The number of sulfurs present, defined by k preferably ranges from 2 to 4. Particularly preferred aromatic sulfide groups are bis-para-(C6H4)xe2x80x94S2xe2x80x94(C6H4)xe2x80x94 and paraxe2x80x94(C6H4)xe2x80x94S2xe2x80x94(C6H5). The diazonium salts of these aromatic sulfide groups may be conveniently prepared from their corresponding primary amines, H2Nxe2x80x94Arxe2x80x94Skxe2x80x94Arxe2x80x2xe2x80x94NH2 or H2Nxe2x80x94Arxe2x80x94Skxe2x80x94Arxe2x80x3.
Another preferred set of organic groups which may be attached to the carbon black are organic groups having an aminophenyl, such as (C6H4)xe2x80x94NH2, (C6H4)xe2x80x94CH2xe2x80x94(C6H4)xe2x80x94NH2, (C6H4)xe2x80x94SO2xe2x80x94(C6H4)xe2x80x94NH2.
Uses of the Carbon Black Products
The carbon black products of this invention may be used in the same applications as conventional carbon blacks. The organic groups attached to the carbon black, however, can be used to modify and improve the properties of a given carbon black for a particular use. If desired these organic groups attached to the carbon black may also be chemically changed using means known in the art into other groups for a particular use. For example, an acid group can be converted to its salt or its amide.
Carbon black products according to the invention have been prepared and evaluated in a number of end use applications. These uses include, for example, plastic compositions, aqueous inks, aqueous coatings, rubber compositions, paper compositions and textile compositions. The following paragraphs describe these uses generally and examples of each are shown below.
The carbon black products of this invention may be used as pigments or colorants in a plastic material. The carbon black products of the invention can also be used to impart conductivity to a plastic material. The carbon black products of the invention may give an increased rate of dispersion or improved quality of dispersion over the corresponding untreated carbon blacks. These improvements offer an economic advantage in plastic manufacture and in value of the finished product, respectively. As shown in Examples 47-62, using carbon black products of the invention may improve impact strength of the plastic. Thus, the invention relates to an improved plastic composition comprising a plastic and a carbon black, the improvement comprising the use of a carbon black product according to the invention.
As with conventional carbon blacks, the carbon black products can be used with a variety of plastics, including but not limited to plastics made from thermoplastic resins, thermosetting resins, or engineered materials, for example, composites. Typical kinds of thermoplastic resins include: (1) acrylonitrile-butadiene-styrene (ABS) resins; (2) acetals; (3) acrylics; (4) cellulosics; (5) chlorinated polyethers; (6) fluorocarbons, such as polytetrafluoroethylene (TFE), polychlorotrifluoroethylene (CTFE), and fluorinated ethylene propylene (FEP); (7) nylons (polyamides); (8) polycarbonates; (9) polyethylenes (including copolymers); (10) polypropylenes (including copolymers); (11) polystyrenes; (12) vinyls (polyvinyl chloride); (13) thermoplastic polyesters, such as polyethylene terephthalate or polybutylene terephthalate; (14) polyphenylene ether alloys; and blends and alloys of the above with rubber modifiers. Typical thermosetting resins include: (1) alkyds; (2) allylics; (3) the aminos (melamine and urea); (4) epoxies; (5) phenolics; (6) polyesters; (7) silicones; and (8) urethanes.
Generally, the carbon black product is added like any other pigment to the plastic used to form a plastic premix. This can be done, for example, in a dry mix or a melt stage. The carbon black products of the invention may be used in combination with other conventional additives in plastic compositions. According to the invention, the term plastic composition includes, but is not limited to, any plastic material, article, goods, surface, fabric, sheet, and the like For example, plastic materials include automotive parts, siding for homes, liners for swimming pools, roofing materials, packaging materials, and any variety of other household or industrial items.
The carbon black products of this invention are also useful in aqueous ink formulations. The water-dispersible carbon black products discussed above are particularly preferred for this use. Thus, the invention provides an improved ink composition comprising water and a carbon black, the improvement comprising the use of a carbon black product according to the invention. Other known aqueous ink additives may be incorporated into the aqueous ink formulation.
In general, an ink consists of four basic components: (1) a colorant or pigment, (2) a vehicle or varnish which functions as a carrier during printing, (3) additives to improve printability drying, and the like, and (4) solvents to adjust viscosity, drying and the compatibility of the other ink components. For a general discussion on the properties, preparation and uses of aqueous inks, see The Printing Manual, 5th Ed., Leach et al, Eds. (Chapman and Hall, 1993). Various aqueous ink compositions are also disclosed, for example, in U.S. Pat. Nos. 2,833,736, 3,607,813, 4,104,833, 4,308,061, 4,770,706, and 5,026,755.
The carbon black products of the invention, either as predispersion or as a solid, can be incorporated into an aqueous ink formulation using standard techniques. Use of a water dispersible carbon black product of the invention provides a significant advantage and cost savings by reducing or eliminating the milling steps generally used with other conventional carbon blacks.
Flexographic inks represent a group of aqueous ink compositions. Flexographic inks generally include a colorant, a binder, and a solvent. The carbon black products of the invention, particularly the water-dispersible carbon products, are useful as flexographic ink colorants. Example 101 shows the use of a carbon black product of the invention in an aqueous flexographic ink formulation.
The carbon black products of the invention can be used in aqueous news inks. For example, an aqueous news ink composition may comprise water, the carbon black products of the invention, a resin and conventional additives such as antifoam additives or a surfactant.
The carbon black products of the invention may also be used in aqueous coating compositions such as paints or finishes. The use of the water dispersible carbon black products discussed above in such coating compositions is preferred. Thus, an embodiment of the invention is an improved aqueous coating composition comprising water, resin and a carbon black, the improvement comprising the use of a carbon black product according to the invention. Other known aqueous coating additives may be incorporated the aqueous coating compositions. See, for example, McGraw-Hill Encyclopedia of Science and Technology, 5th Ed. (McGraw-Hill, 1982). See also U.S. Pat. Nos. 5,051,464, 5,319,044, 5,204,404, 5,051,464, 4,692,481, 5,356,973, 5,314,945, 5,266,406, and 5,266,361.
The carbon black products of the invention, either as a predispersion or as a solid, can be incorporated into an aqueous coating composition using standard techniques. Use of a water dispersible carbon black product provides a significant advantage and cost savings by reducing or eliminating the milling steps generally used with other conventional carbon blacks. Examples 102 and 103 below show the use of carbon black products according to the invention in aqueous automotive topcoat formulations.
The carbon black products of the invention may also be used in paper compositions. Preferred carbon black products for this use are the water dispersible carbon black products discussed above. Accordingly, the invention relates to an improved paper product comprising paper pulp and a carbon black, the improvement comprising the use of a carbon black according to the invention.
The carbon black products of the invention, either as a solid or a predispersion, can be incorporated into paper pulp using standard papermaking techniques as with conventional carbon blacks. Use of a water dispersible carbon black product discussed above may provide a significant advantage and cost savings by reducing or eliminating the steps generally used to disperse other conventional carbon blacks. Example 100 shows a paper product using a carbon black product according to the invention.
The paper products of the invention may incorporate other known paper additives such as sizing agents, retention aids, fixatives, fillers, defoamers, deflocculating agents, and the like. Advantageously, the water dispersible carbon black products discussed above are retained more efficiently at low loading levels when compared to the untreated carbon black when retention aids and acidic or alkaline sizing agents are used.
The carbon black products of the invention may also be used, as with conventional carbon blacks, as pigments, fillers, and reinforcing agents in the compounding and preparation of rubber compositions. Accordingly, the invention relates to an improved rubber composition containing rubber and a carbon black, the improvement comprising the use of a carbon black product according to the invention. The properties of the carbon black are important factors in determining the performance of the rubber composition containing a carbon black.
Carbon blacks, for example, are useful in the preparation of rubber vulcanizates such as those in tires. It is generally desirable in the production of tires to utilize carbon blacks which product tires with satisfactory abrasion resistance and hysteresis performance. The treadwear properties of a tire are related to abrasion resistance. The greater the abrasion resistance, the greater the number of miles the tire will last without wearing out. The hysteresis of a rubber compound means the difference between the energy applied to deform a rubber compound, and the energy released as the rubber compound recovers to its initial undeformed state. Tires with lower hysteresis values reduce rolling resistance and therefore are able to reduce the fuel consumption of the vehicle utilizing the tire. Thus, it is particularly desirable to have carbon black products capable of imparting greater abrasion resistance and lower hysteresis in tires.
The carbon black products of this invention are useful in both natural and synthetic rubber compositions or mixtures of natural and synthetic rubbers. Carbon black products containing aromatic sulfides as the organic group, which are discussed above, are preferred for this use. Particularly preferred for use in rubber compositions are carbon black products having an attached aromatic sulfide organic group of the formula -(C6H4)-Sk-(C6H4)-, where k is an integer from 1 to 8, and more preferably where k ranges from 2 to 4. The carbon black products of the invention can be used in rubber compositions which are sulfur-cured or peroxide-cured.
The carbon black products may be mixed with natural or synthetic rubbers by normal means, for example by milling. Generally, amounts of the carbon black product ranging from about 10 to about 250 parts by weight can be used for each 100 parts by weight of rubber in order to impart a significant degree of reinforcement. It is, however, preferred to use amounts varying from about 20 to about 100 parts by weight of carbon black per 100 parts by weight of rubber and especially preferred is the utilization of from about 40 to about 80 parts of carbon black per 100 parts of rubber.
Among the rubbers suitable for use with the present invention are natural rubber and its derivatives such as chlorinated rubber. The carbon black products of the invention may also be used with synthetic rubbers such as: copolymers of from about 10 to about 70 percent by weight of styrene and from about 90 to about 30 percent by weight of butadiene such as copolymer of 19 parts styrene and 81 parts butadiene, a copolymer of 30 parts styrene and 70 parts butadiene, a copolymer of 43 parts styrene and 57 parts butadiene and a copolymer of 50 parts styrene and 50 parts butadiene; polymers and copolymers of conjugated dienes such as polybutadiene, polyisoprene, polychloroprene, and the like, and copolymers of such conjugated dienes with an ethylenic group-containing monomer copolymerizable therewith such as styrene, methyl styrene, chlorostyrene, acrylonitrile, 2-vinyl-pyridine, 5-methyl 2-vinylpyridine, 5-ethyl-2-vinylpyridine, 2-methyl-5-vinylpyridine, alkyl-substituted acrylates, vinyl ketone, methyl isopropenyl ketone, methyl vinyl either, alphamethylene carboxylic acids and the esters and amides thereof such as acrylic acid and dialkylacrylic acid amide; also suitable for use herein are copolymers of ethylene and other high alpha olefins such as propylene, butene-1 and pentene-1.
The rubber compositions of the present invention can therefore contain an elastomer, curing agents, reinforcing filler, a coupling agent, and, optionally, various processing aids, oil extenders, and antidegradents. In addition to the examples mentioned above, the elastomer can be, but is not limited to, polymers (e.g., homopolymers, copolymers, and terpolymers) manufactured from 1,3 butadiene, styrene, isoprene, isobutylene, 2,3-dimethyl-1,3-butadiene, acrylonitrile, ethylene, propylene, and the like. It is preferred that these elastomers have a glass transition point (Tg), as measured by DSC, between xe2x88x92120xc2x0 C. and 0xc2x0 C. Examples of such elastomers include poly(butadiene), poly(styrene-co-butadiene), and poly(isoprene).
Advantageously, the carbon black products of the present invention can impart improved abrasion resistance and/or reduced hysteresis to rubber compositions containing them. Examples 104-116 show the use of carbon black products of the invention in various rubber compositions and various properties of those compositions.
The carbon black products of this invention may also be used to color fibers or textiles. Preferred carbon black products for this use are the water dispersible carbon black products discussed above. Accordingly, the invention relates to improved fiber and textile compositions comprising a fiber or textile and a carbon black, the improvement comprising the use of a carbon black according to the invention. Fibers suitable for use comprise natural and synthetic fibers such as cotton, wool, silk, linen, polyester and nylon. Textiles suitable for use comprise natural and synthetic fibers such as cotton, wool, silk, linen, polyester and nylon. Preferably natural fibers and textiles comprising cotton, wool, silk and linen are used.
The carbon black products of the present invention may be colored by means known in the art to color fibers and textiles with, for example, direct and acid dyes. For a general discussion of coloring with dyes, see Kirk-Othmer Encyclopedia of Chemical Technology, Vol 8 pp 280-350 xe2x80x9cDyes, Application and Evaluationxe2x80x9d (John Wiley and Sons, 1979). Use of a water dispersible carbon black product discussed above provides a method for coloring these materials with a lightfast colorant.
The following examples are intended to illustrate, not limit, the claimed invention.